The Bible teaches that believers can have unbelieving friends but should be careful of ungodly influences.
Paul used the phrase "unequally yoked" in his second letter to believers in Corinth (2 Corinthians 6:14). The term is most often used when discussing partnerships, usually marriage. It could also apply to very close friendships, but it doesn't necessarily have to. Believers can be a good influence on unbelieving friends (Matthew 5:13-15), but the reverse may also be true (Proverbs 12:26, 13:20, 22:24-25, 27:17). In fact, Paul also warned of the danger of being corrupted by those one keeps company with (1 Corinthians 15:33).
Jesus associated with sinners, but with the goal of bringing them to repentence (Luke 7:34). Believers can have unbelieving friends, but they should never compromise on truth and godliness in such relationships.
If everyone were jumping off a cliff, would you jump off, too?
If you heard that as a kid, you were probably trying to get your parents to agree to let you do something that all your friends were doing, something that wasn't in your best interests.
Sometimes, we still act like kids but in adult bodies. And we may still have friends that want us to do what we shouldn't. Maybe it's as simple as going to a see a movie that has suggestive scenes, gossiping about other people you know, or spending money frivolously. Believers who have unbelievers as friends should be leading them up rather than following them down.
That same principle is really what Scripture is getting at when it warns about influence: not isolation but direction. Every voice you allow into your life shapes your heart, mind, and habits, almost without you noticing it. That’s why wisdom is necessary. It's not about avoiding people but about recognizing patterns: who tends to pull you closer to Christ and who consistently pulls you away from Him? How much influence are you allowing those who aren't running the race of faith to have in your life?
Real friendship doesn’t just go along with everything; it cares enough to resist what’s harmful, even when it’s uncomfortable. In that sense, being a faithful friend sometimes means being the one person willing to say, “I’m not following that—but I’m still here with and for you.”